Van der Waals epitaxy

Koma A 1992 Van Der Waals epitaxy—a new epitaxial growth method for a highly lattice mismatched system Thin Soiid Fiims 216 72-6... 

Non-epitaxial electrodeposition occurs when the substrate is a semiconductor. The metallic deposit cannot form strong bonds with the substrate lattice, and the stability conferred by co-ordination across the interface would be much less than that lost by straining the lattices. The case is the converse of the metal-metal interface the stable arrangement is that in which each lattice maintains its equilibrium spacing, and there is consequently no epitaxy. The bonding between the met lic lattice of the electrodeposit and the ionic or covalent lattice of the substrate arises only from secondary or van der Waals forces. The force of adhesion is not more than a tenth of that to a metal substrate, and may be much less. 

Graphite and carbon fibers have been used at templates. Thus, nylon 6 has been polymerized on a graphite matrix. Such syntheses of polymers in the presence of a solid template, where the solid acts as a template have been described as polymerization-induced epitaxy (PIE). The monomer and resulting film is adsorbed on the template surface through only van der Waals forces. After polymerization, the polymer is washed from the template. The recovered polymer retains special structural features introduced by the template. 

Koma, A., New epitaxial growth method for modulated structures using Van der Waals interactions. Surf. Sci., 267, 29, 1992. 

The easy electron migration from platinum crystallites to the biphasic support clearly indicates that a coherent interface between the metal and the substrate must also be considered. Fig.8 shows the superposition of the electron diffraction pattern from the [Oil] zone axis of platinum with a simulated diffraction pattern for the support. The good matching between several reciprocal vectors of the two structures indicates that the relationship between the platinum and the support is similar to that noted in previous observations on the epitaxial relationship between Pd[0lT] zone axis and Y-AI2O3 [110] zone axis (Ref. 23). According to Dexpert et al. (Ref. 23), the resistance to sintering can, therefore, be interpreted as the result of the strength of the epitaxial interactions which is intermediate between chemical bonds and Van der Waals forces. 

Figure 2. Schematic representation of principal surface sorption processes, (a) Projection of the CoOOH structure in the ab plane. MSC, multinuclear surface complexation represented by an epitaxy of a-FeOOH (left) ISC, mononuclear monodentate (middle right), mononuclear bidentate (top right) and binuclear bidendate (lower right) inner-sphere complexation OSC, outer-sphere surface complexation (top) LD, lattice diffusion (center), (b) Example of epitaxy without sharing of oxygens (Van der Waals forces). The. ..AB-AB... close-packed anionic layer sequence of Co(OH)2(s) is coherently stacked on the. ..AB-BC-CA... layer sequence of CoOOH. Co(OH)2(s) has a 1H polytypic structure, and CoOOH a 3R. Small circles are...

The chemistry and structures of SAMs of alkanethiolates on gold have been extensively studied, and need not be reviewed here [44]. In brief, when fully equilibrated and in their most stable form, these SAMs seem to be two-dimensional quasicrystals, with the sulfur headgroups epitaxial on the gold surface. A 30° tilt of the trans-extended alkane chains brings these chains into van der Waals contact. Functional groups present on the termini of the chains are exposed to the solution. Conformational disorder in the system is concentrated in the terminal regions of the chains. 

Inumaru K., Nakajima H., Ito T., Misono M. Porous aggregates of unidirectionaUy oriented (NH4)3PWi2O40 microcrystallites Epitaxial self-assembly. Chem. Lett. 1996 7 559-560 IsraeladiviH J.N., Tabor D. The measurement of van der Waals disprasion forces in the range 1.5-130 nm. Proc. Roy. Soc. (London) A 1972 331 19-38 Israelachvih J.N., Tahor D. van der Waals forces Theory and expaiment. Prog. Surf. Membr. Sd. 1973 7 1-55... 

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